Electrohydraulic operator



Mud: 16, 1943. E. a ARNOLD 2,313,909

ELECTROHYDRAULIC OPERATQR Original Filed March 25. 19:9

I L. 017 level ATTORNEY Plasma 16. 1943 2,313,909

ELECTROHYDRAULIC OPERATOR- Edwin E. Arnold, Pittsburgh. Pa, alsignorto Westinghouse Electric & Manufacturing Oom- .-pany. East Pittsburgh, Pa, a corporation of Pennsylvania Original application March 28, 1939, No.

263,734. Divided and this application June-18, 1941, Serial No. 398,513

2 Claims.

My invention relates to an electro-hydraulic operator, and more specifically to a specific type of hydraulic pump which is operated by the ro- .tative eifort of the shaft of an electric motor and which is useful, for example, to develop hydraulic pressure for eil'ecting a linear thrust to operate a clutch, brake, door, or any other similar load device.

My present application is a division of my copending application Serial No. 263,734, filed March 23, 1939, entitled "Electra-hydraulic operators.

One object of my invention is to provide a viscosity screw-type pump which is capable of developing considerable pressure for a relatively ple, compact, rugged, and relatively small: yet

which is capable of developing a high fluid pressure and, therefore, capable of employing a relatively small working piston area with consequent reduction in overall size.

A further object of my invention is to provide a reversely threaded viscosity type pump to avoid leakage at the .seal formed with the pump casing.

Other objects and advantages will become more apparent from a study of the following specification, when considered in conjunction with the accompanying drawing, in which:

Figure l is a side view partly in cross-section, of a device embodying my invention;

Fig. 2 is a sectional view, taken along line 11-11 of Fig. 1; and

Fig. 3 is a partial view of a modification of a rotor embodying my invention.

Referring to Figure l, numeral i denotes a casing which is partially filled with a fluid such as oil or the like. Fastened to the top of the casing is a cover member 2 upon which is mounted anelectric motor 3, which drives a drive shaft 4. The drive shaft 4 has operatively connected thereto a substantially cylindrical solid boss member or rotor 5, which telescopically fits into a substantially cylindrical sleeve 6. This sleeve is insertable through an opening in the bottom of the casing and is removably secured to partition member 24 by a screw-threaded connection. Along the outer surface of the rotor 5 is a comparatively small and'shallow, doubly wound or bifilar helical groove 1 which communicates with the upper or inlet chamber 3| and with an enlarged opening 8 in the rotor 5, which opens in registry with an opening 9 in the sleeve 6 which, in turn, is in communication with a pressure or working chamber ll situated at the bottom of said casing. Although the groove is described as being a double helix, it ,may likewise be a single helix, triple helix, or, in fact, any number of helices and of any desirable cross-section.

For example, referring to Fig. 3, a single helical groove 1' is shown. As shaft 4' rotates rotor 5' within sleeve 8', groove I picks up oil from the upper chamber 3i and because of the tendency of the oil to cling to the rotor due to its viscosity, it is propelled through the helical groove and it finally emerges from openings 8 and 9 into the pressure or working chamber wherein the oil develops a high fluid pressure, It will be noted that the oil is fed into the device shown in Fig. 3, by gravity. A greater pressure may be developed if the oil is fed under pressure, for example, as shown in Figs. 1 and 2.

Rotor I has on the top thereof a'cylindrical portion Ia which is for the purpose of. obstructing the passage of oil directly into the helical grooves. The oil is allowed to enter only through holes Shin cylindrical portion Ia (see Fig. 2), thence the oil by centrifugal force is impelled radially outwardly along radial grooves 50' of rotor 5 emerging into the diametrically opposite starting points of the two helical grooves. Inasmuch as there is a great tendency for the oil, because of its pressure developed in opening 3, to leak along the surface of the lower rotor portion 5d and develop a pressure at the bottom'of member 8, such portion 5d is provided with a helica1 groove which is wound opposite to groove I, therefore, which will tend to move the oil upwardly and counterbalance this leakage tendency. To further counterbalance leakage, shaft 4 and rotor 5 are provided with a hole 4a which extends throughout their length and forms a bypass between the space at the bottom of rotor po tion 5:! and the upper chamber 3i through a re. ial hole 4b, which extends through shaft 4 thereby, in effect, equalizing the pressure at the bottom of rotor portion 5d with that in chamber 3i, which chamber is at substantially atmospheric pressure. A collar 38 is screw-threaded to the lower part of a portion of shaft 4, the lat-' -ter being of slightly reduced diameter and extending through rotor 5. The bottom of cylindrical sleeve 8 is closed by means of a screwthreaded plugia. A second substantially cylindrical sleeve is also removably secured to partition member 24 and projects through the lower part of the casing. Sleeve il telescopically surrounds a piston l2 having rings I3 and a thrust fluid-tight gasket 26. Thus it will be seen that the return spring i8 normally urges pistonl2 in the downward direction, which downward movement is arrested by a partially threaded stop member 2| which is screwed into the bottom portion of the casing and a bufier spring 212 which is rigidly connected to a boss 23 which is formed integral with piston I2, which spring is for the purpose of absorbing shock and forming a cushion or resilient stop for the piston as it completes its return or down stroke.

Partition member 24 which forms one of the walls of the pressure chamber III, has a threaded hole therethrough into whichis threaded a portion 25 of an electromagnetically operated bypass valve 26. Valve 26 comprises a magnet coil 21 which is energized by wires 23 which are lead into the casing through a lead-in conductor 29, which is preferably connected with the motor circuit of motor 3 (not shown) so that the magnet will become energized at the same time motor 3 is energized and deenergized when the motor is deenergized. A by-pass port 30 is adapted to provide fluid communication between pressure chamber l and the upper chamber or intake chamber 3| when the magnet coil 21' is deenergized so as to permit the opening of the by-pass by a spring 32. When the magnet is energized. however, it attracts its armature and plunger 33 which is connected to the armature, thus effecting movement of the valve so as to close or at least restrict the by-pass port 30. The oil now goes up through passage 34 through holes 35 but,can go no further due to the closure or seating of valve 33.

The operation of the device is as follows. Whenthe motor 3 and magnet coil 21 are simultaneously energized, drive shaft l'will rotate, thus rotating the rotor 5, the latter propelling fluid through its helical groove I from the intake chamber 3| along the sleeve member 6 to openings 8 and 9, finally into the pressure chamber It, in which chamber a considerable pressure is produced by virtue of the high output characteristic inherent in a viscosity screw pump. The fluid pressure in chamber l0 acts on the working surface of piston l2 causing an upward movement of the piston against the restraining action of the return spring l8 and, in turn, causing an upward movement of thrust rod H which furnishes a power stroke for any suitable load device (not shown) such as a brake.

During this time, the electromagnetically operated by-pass valve 26 is closed, hence the fluid is confined in the pressure chamber Ill and its laterally communicating passages. After the completion of the upward or power stroke of the thrust rod l4, motor 3 and coil 21 are deenergized, thus the rotation of member is arrested and the by-pass valve 26 is opened by spring 32. Return spring l8 now forces the piston i2! downwardly, displacing fluid from the pressure: chamber I0 upwardly through helical grooves: I and finally into the upper or inlet chamber 3]. An-

' down stroke of the piston.

other path of fluid for the chamber i 0 is through the port 30, which is now open, of the valve 26. The primary purpose of the by-pass valve 26 is to allowa larger fluid flow between the pressure chamber l0 and-the inlet chamber 3| when the pump ceases to develop pressure in chamber l0,

so as to allow a quick downward return of the piston. While the helical groove 1 in itself forms a by-pass between chambers l0 and 3|, the groove is so small that the rate of flow oi fluid therethrough would be comparatively small, thus requiring an appreciable length of time for the It is within the scope of my invention to make electric motor 3 reversible so that after the upward movement or power stroke of the thrust rod H, the motor may be plugged or reversed, thereby reversing the direction of rotation of the rotor 5, the effect of this reversal of rotation being to considerably increase the rate of flow of fluid from chambers l0 through groove 1 to chamber 3|, thus considerably increasing the by-pass effect of the helical groove I, thus decreasing the time required for the down stroke of the piston. The electromagnetically operated by-pass valve 26 may or may not be used simultaneously, depending on the time element desired for the completion of the return stroke or down stroke of the thrust rod I 4.

The viscosity screw type of pump as described, is not as efllcient as the propeller type of pump, such as shown and described in my copending application, Serial No. 257,940, flied February 23, 1939, entitled FElectro-hydraulic operators, and assigned to the Westinghouse Electric & Manufacturing Company, because of the large frictional losses inherently present in a viscosity screw type of pump. However, the pressure developed by the viscosity screw type pump as compared to the pressure developed by a similarly sized propeller, or even centrifugal type of pump, is enormously greater, partly due to the high rotational speeds obtainable by electric motors which thus impart a high velocity to the fluid in the screw or groove, particularly the layer of fluid immediately adjacent the surface of the groove formed in the rotor. Pressures above 1,000

pounds per square inch, for example, may be developed by a viscosity screw type pump as compared with pressures in the neighborhood of 15 pounds per square inch of a similarly sized ordinary propeller or centrifugal type of pump. It will thus be seen that an electro-hydraulic operator embodying the above screw pump is readily adapted in situations where space limitation is severe and where considerable force as a lied by a thrust load is required, such as in large capacity brakes and the like. A wide and varied number of applications of the above-described device is obvious, such for example, as hoist clutches and brakes, machine presses, door operators, feeding machines, etc.

I am, of course, aware that others, particularly after having had the benefit of the teachings of my invention, may devise other forms of electrohydraulic operators embodying my invent;on, and I, therefore, do not wish to be limited to the specific showings made in the drawing and the descriptive disclosure hereinbefore made, but wish to be limited only by the scope of the appended claims and such prior art that maybe pertinent I claim as my invention:

1. A rotary viscosity pump comprising, incombination, a stationary cylindrical sleeve, a cylindrlcal body rotatably disposed within said sleeve and a shallow groove on the surface of one oi.

said cylindrical members, an oil supply; conduit means for feeding said oil supply substantially along the axis of said cylindrical rotary body and into said shallow groove for eil'ecting cen trifugal priming of said pump and ring means formed on said cylindrical rotary body closely fitted to said sleeve for confining oil in said groove so as to develop high pressure therein and to prevent ingress of oil thereto except through said conduit means.

2. A rotary viscosity pump comprising, in combination, a stationary cylindrical sleeve, a cylindrical body rotatably disposed within said sleeve,

an oil supply, a helically spiral shallow groove on the peripheral suriace oi said body for propelling oil longitudinally of said sleeve by viscosity action, an inlet groove formed in said cylindrical body for introducing oil first axially of said body and then radially thereof at one end so as to effect priming of said pump by centriiugal action when said body is rotated and ring means formed on said cylindrical rotary body closely fitted to said sleeve for confining oil in said groove so as to develop high pressure therein'and to prevent ingress of oil thereto except through said conduit means.

EDWIN E. ARNOLD. 

